It has been known for many years that a substantial danger exists in the operation of firearms and particularly shotguns where a small diameter cartridge can become lodged in the barrel of a gun designed to handle larger diameter cartridges. This is particularly a problem where the user of a given collection of firearms has certain standard diameter cartridges for a smaller firearm which may become lodged in the barrel of a larger diameter firearm.
For instance, the owner of 12 and 20 gauge shotguns may accidentally insert a 20 gauge cartridge in the 12 gauge shotgun. The 20 gauge cartridge is small enough to pass through the ignition chamber of a 12 gauge shotgun, but large enough that it will lodge in the barrel of the shotgun and not pass all the way through. Instances have occurred where a 12 gauge shotgun barrel is blocked in this way and a 12 gauge cartridge is subsequently discharged into the blocked barrel with disastrous results.
The problem occurs with many different sized cartridges, but it is particularly serious with 12 and 20 gauge shotguns because many shooters prefer to use 20 gauge shotguns for skeet shooting and 12 gauge shotguns for hunting.
It is an object of this invention to prevent a shotgun barrel from becoming blocked with a cartridge which is smaller in diameter than the size cartridge for which the barrel is designed.